Custom Category Template

I am trying to display posts by groups with each group/category having it’s own header image and template. In my index.php file for my master template, I have the following:

<?php
if (is_home())
{
	include (TEMPLATEPATH . "<?php echo get_settings('home'); ?>/wp-content/themes/simpla/postlisting_home.php");
}
else if (is_category('3')) {
    include (TEMPLATEPATH . "<?php echo get_settings('home'); ?>/wp-content/themes/simpla/postlisting_news.php");
}
else if (is_category('4')) {
    include (TEMPLATEPATH . "<?php echo get_settings('home'); ?>/wp-content/themes/simpla/postlisting_media.php");
}
else {
    include (TEMPLATEPATH . "<?php echo get_settings('home'); ?>/wp-content/themes/simpla/postlisting_misc.php");
}
?>

Basically I am trying to get it so that if it is home, it uses a specfic template. If the page has posts for category 3, use the specified template, etc. However the above codes displays nothing. (All four template files exist and are correct.) I don’t receive any error message at all.